Delay Tolerant Routing for Cognitive Radio Vehicular Ad Hoc Networks

Cognitive Radio Vehicular Ad Hoc Networks (CRVANETs) can resolve the conflicts between limited spectrum resource and vehicular communication service needs, and thus it receives much concern. Most existing routing solutions for Cognitive Radio Ad Hoc Networks (CRAHNs) or VANETs cannot be directly applied to CR-VANETs due to the high mobility of vehicles and varying availability of spectrums. To fill this gap, with the proliferation of delay tolerant applications, this paper presents a delay tolerant routing strategy for CR-VANETs with the object of maximizing the packet delivery ratio from the source to the destination. The proposed routing scheme is composed of two parts: the routing policy and the message replication policy. In the first policy, we select a concurrent forwarding set under the restriction of CR spectrum holes, and choose an optimized routing path for the next hop. In the second policy, we propose a hybrid and adaptable method relying on Drop-Oldest and Drop-Most strategies, to reduce the delivery cost. Through extensive simulations, we demonstrate that the proposed delay tolerant routing mechanism provides with better packet delivery ratio compared to state-of-the-art protocols.